1. Field of the Invention
The present invention relates to a magnetic head. More particularly, the present invention pertains to a magnetic head for use in a magnetic disk system.
2. Description of the Prior Art
FIG. 5(a) is a perspective view of a conventional magnetic head used in a magnetic disk system; FIG. 5(b) is an enlarged view of that part of the magnetic head shown in FIG. 5(a) which is encircled by the chain line; and FIG. 6 is a perspective view of the head core shown in FIG. 5(a). Referring to these figures, the reference numeral 10 denotes a head core which comprises a read/write core 11, a center core 12 and an erase core 13. These core members are made of a magnetic material, for example, ferrite. The reference numeral 20 denotes a read/write gap which is defined between the read/write core 11 and the center core 12 which are bonded together by means of glass 40. The read/write gap 20 enables information to be stored onto and regenerated from a magnetic recording medium. The reference numeral 30 denotes an erase gap which is defined between the erase core 13 and the center core 12 which are bonded together by means of glass 41. The erase gap 30 is adapted to provide a predetermined portion carrying no data (known as a "guard band") between adjacent tracks in order to ensure interchangeability of the information recorded on a magnetic recording medium at the read/write gap 20. The reference numerals 50 and 60 denote non-magnetic reinforcing members which sandwich the head core 10 therebetween. The non-magnetic reinforcing members 50 and 60 are made of a ceramic material, for example, calcium titanate or barium titanate. It should be noted that the read/write core 11 and the erase core 13 are, although not illustrated, each provided with a coil for generating electromagnetic force.
The sliding surface [indicated by the hatched lines in FIG. 5(a)] that is defined by the head core 10 and the non-magnetic reinforcing members 50 and 60 so as to come into sliding contact with a magnetic recording medium is formed by lapping the contact surface with high accuracy after the head core 10 and the non-magnetic reinforcing members 50 and 60 have been bonded together.
The dynamic characteristics of a magnetic head are greatly affected not only by the gap accuracy but also by the depth of the gap. In many conventional magnetic heads having the above-described structure, however, the non-magnetic reinforcing members 50 and 60 are opaque and it is therefore impossible to visually observe the depth of the gap and hence impossible to directly know the gap depth when the surface for contact with a magnetic recording medium is being lapped with high accuracy. For this reason, the gap depth has heretofore been controlled by electromagnetically measuring the level of inductance. However, this conventional method needs a complicated measuring process and does not enable direct measurement; therefore, the gap depth cannot be controlled with high accuracy.
To solve this problem, a magnetic head wherein non-magnetic reinforcing members are made of a light-transmitting material, for example, glass, has been proposed (see Japanese Utility Model Public Disclosure (KOKAI) No. 60-173109). However, glass or other light-transmitting material is less effective to serve as reinforcing members, as it wears at a high rate and is readily damaged by dust or the like. If the reinforcing members are damaged, the reliability with respect to a disk as being a magnetic recording medium is deteriorated, which leads to data read errors or other problems. Further, since there is a difference in the wear rate between glass and the ferrite core, the configuration of the magnetic head eventually changes, causing a change in the floating characteristics. As a result, the condition of contact between the head and the disk changes, thus causing signals to be weakened.